The present invention relates to signal isolators and, particularly, signal isolators that operate according to an on-off keyed signal protocol.
Isolators are devices that exchange data signals between two galvanically isolated circuit systems. The two circuit systems each operate in different voltage domains, which may include different supply voltages and different ground references. Isolation devices may provide data exchange across an isolation barrier, which maintains the galvanic isolation. Typical isolation devices include micro-transformers, capacitors, magneto-resistors/giant magneto-resistors and opto-electronic devices.
On-off keying (“OOK”) is a signaling protocol that identifies a digital state of input data based on the type of signal that is transmitted through the isolation barrier. A first digital data state (say, a digital “1”) might be signaled by transmitting a periodic signal across the isolation barrier. A second digital data state (a digital “0”) might be signaled by transmitting no signal across the isolation barrier. A receiver circuit would detect the presence or absence of the periodic signal and decode a digital output signal therefrom.
OOK-based signal isolators typically have inefficient designs. For example, isolator receivers may include a multiplier (or mixer) and an integrator as an energy detector for OOK demodulation. A mixer, however, has a limited ability to handle common mode noise. Integrators typically are very slow for applications that require high data rate transmission across the isolation barrier.
Accordingly, the inventors perceive a need in the art for an improved receiver that provides improved speed and improved noise immunity.